The instant invention relates to buckle chute folders for folding one or more sheets of paper, and more particularly to the folding rollers used to impart a crease to the sheets of paper.
Buckle chute paper folders employing folding rollers are well known. The sheet of paper is fed by a first pair of feed rollers up into a buckle chute, which stops the forward progress of the paper sheet and causes a buckle to be formed. The buckle is then forced to enter the nip of a pair of folding rollers (one of which may be one of the feed rollers) which impart a crease in the buckle. The folding rollers then continue to feed the folded sheet toward a pair of exit rollers or another buckle chute for forming a second fold.
Buckle chute folders are used to fold single sheets and a plurality of sheets. The folding rollers are biased toward each other, and can be adjusted to generate the optimum pressure for a given number of sheets to be folded at once. Obviously, an optimum pressure for folding a packet of ten sheets would not be an optimum pressure for folding a single sheet. Thus, when a buckle chute folder is being used to fold various numbers of sheets in succession, some of the packets will not be folded as well as some other packets depending on the adjustment of the pressure for the folding rollers.
Because the conventional folding rollers are biased toward each other with springs, there is a limit to the number of sheets which can be folded at one time, which generally is about 12 sheets.
The instant invention overcomes the foregoing problems and provides a pair of folding rollers which will fold thin collations as well as thick collations and not derogate from the quality of folding because of variations in the thickness of the packet being folded. The instant invention also increases the number of sheets which can be folded in a single packet over the number which can be folded by conventional folding rollers. Thus, the instant invention provides improved quality in buckle chute folding and increases the number of sheets which can be folded by buckle chute folders while retaining the ability to fold a single sheet.